Building a new engine

[rosscla]

Before


After


Had to leave a little metal near the back stud as this manifold is designed for either spacing

[barnsleybilly]

Also I have a spare front drum hub knocking around. I'm wondering if I can take the shoes and pins etc from it and fit them my new engine?

In a word no, the pins are cast into the front hubs and if you swap shoes between different hubs they'll need bedding in all over again due to minor differences in the two hubs.

The indian makino shoes are good and only cost about £8 a set.

[Snails]

Thanks. I'll reuse the items from my existing engine in that case and hub can go on ebay for funds

[nelson pk]

Not being funny but that looks mighty thin between the port work and inlet stud hole.....I think the gasket will struggle to seal that. I would not use it to be honest. I would hate for you to put that on and then the engine seizes because of an air leak.
Looks less than 1 mm sealing area from your pic?

[rosscla]

Not being funny but that looks mighty thin between the port work and inlet stud hole.....I think the gasket will struggle to seal that. I would not use it to be honest. I would hate for you to put that on and then the engine seizes because of an air leak.
Looks less than 1 mm sealing area from your pic?

I'll silicone it and test it, but might also plug in to the 200 spacing.

[Snails]

I've made some adjustment to the inlet port (pictured) and inlet manifold and I'm happy with the results. I still need to use the dremmel sanding attachment and a bit of wet and dry to finish them off.

before


after


I've moved on to looking at the exhaust port. I decided to remove the exhaust now rather than later as the weather is so poor its probably the best time to take it off the road.

I'm not sure what to do. The existing gasket is made of copper and its inner bore is less than that of the down pipe



I have some replacement card gaskets that have a larger bore than my down pipe



Do I

a. stick with the copper gasket and use that as the template for cleaning up the SR barrel port. I'd have to accept that its being limited to some degree.
b. Use the new gasket as the template and not worry that the exhasut bore is smaller
c. Use the new gasket and modify the down pipe too, which should provide maximum results. It looks like quite a lot of metal to take off in the picture but I think i can safely take off most of it without it going wider than the actual pipe part of the pipe (if that makes sense)

Its a AF Clubman small bore

[olliewtf]

Looks to me like you have a standard gasket on there. Get a big bore type. On my build im going to go for the fibre gasket from MB, it is supposedly a little more lenient on warped manifolds, and no matter how much i try, my manifold always leaks a little. I wouldnt cut in to the manifold as I dont think theres enough meat there before breaking into the weld, but thats your choice.
In terms of your inlet port, dont polish it to a mirror finish as petrol can pool on the surface causing heat build up, smooth but not too smooth! Worry more about polishing the exhaust port for good gas flow.
As to rear hub bearings, im going through the same thing, theyre bluddy pricey! I messaged MB as their RT bearings are affordable and look really good, but theyll be out of stock for the foreseeable future so i asked what he recommended at a similar price point and he said he's using genuine SIL rear hub bearings on his builds. (scooter restorations!)

It seems to me youre quite comfortable with the dremel, so why dont you consider making a port map and seeing what your port timings are like? Its not as bad as you think, I did mine for the first time with good results, and now i know a bit more Im going to have another go. I have an SR barrel too, and although timings vary form barrel to barrel, mine were conservative. Why not post up your spec and I could give you a good starting point? PM me if you want more info on carrying this out, i highly recommend it and believe you'd be more than competent to do it. I also found that setting up the squish correctly was impossible without machining, which is something I will now address, so dont neglect this! And ive decided im going to fit a 60mm crank with 110 rod (doing a suzuki conversion) so consider if your going to get the rank machined, what yuo could do to improve on it. a longer rod will give you a smoother engine, and will allow greater scope to play with port timings.
Either way, good luck with it!

[olliewtf]

also even if you dont touch your port timings, which i think you should, chamfer the edges, as the transfers in particular on my barrel were razor sharp. if youre not too confident with the dremel inside the barrel, consider just using some sand paper to smooth them off a bit.

[Snails]

Thanks, I did not realise that the port timings varied. The information I had suggested that the port timings were 'ok' and so did not need touching, I may not touch them anyway but I'm interested to discover what they are. How do you create a port map? You dont have a link that explains it do you?

I think that the second gasket i have (the cardboard type) is probably big bore. I seem to remember them being so when I bought them

[olliewtf]

Youre right the card one is big bore. I used a card one once but wasnt impressed, didnt seal very well, but you amy find yours is fine.
From what ive read, most barrels vary in timing, the mugello being a good example, but I have no experience with them so wouldnt want to say, but if you read MBs tech articles on tuning there is a real wealth of information that will get you started. He also had a hand in the SR barrel, and the article he wrote on them says that the porting was very poor, varying from barrel to barrel. at the end of the day, its a cheap and cheerful kit, most people who own them will play with them and get great results. theyre a hell of alot cheaper than other smallblock kits, and really, if you want the best out of your set up, I dont think there are many smallblock kits that are fit and forget! Mugello's seem to have a few problems with timings being way off on certain versions requiring alot of work and potentially the use of longer conrods and packers to make the timings work.
They also have a nikasil bore so the minute you start dremel ing it needs replating, as far as i understand it, but could be wrong.
Casa kits are well made but very conservatively ported, for me it begs the question why buy a go faster kit if it doesnt go that fast? but they are supposedly very well built so a true bolt on kit.
Imolas again require alot of attention to set up, and with this i mean that because of the horse power it can produce, it too is not a bolt on kit, you need to consider every part of your engine, brakes and suspension before fitting.

My point here is that actually, when you delve into it, nothing is truly bolt on. if you want the best out of what youve got, you need to consider everything as a cohesive whole, and check and recheck that everything is as it should be. (this idea leads from me getting a little frustrated on some facebook groups where people are having running problems, or feel they should be getting more power, and rather than looking at their set up in terms of port timing, squish, combustion cc etc. people just say, get a mugello, get an imola. thats pretty poor and useless advice, particularly the imola part, as someone could easily bolt that on an old crank and a knackered drive chain and your asking for trouble!)

So, after drifting off topic, go the extra mile, check your port timings, ask for advice on them, set the squish properly and cover every base.
Its not as hard as it sounds, and youll feel alot better when its all bolted together!

to creat a port map, you are essentially measuring the distance between the top of your barrel, to the top of the exhaust and transfers, and the bottom of the inlet. The best way is to insert a roll of card/paper, and shade over the ports. the edges of the ports will show up, allowing you to measure down. The shape and width and area also comes into play, but maybe thats for another day. Use Eden's fantastic online calculator at lambretta images archive (google it) and put in all your figures to work out the timings.


(disclaimer: I have no experience of any of the kits mentioned, my point was more that actually when people face problems with certain aspects of their engines, they should consider all the factors as explained above rather than just going out and buying another kit. Also the assumption that a 400 pound kit will simply bolt on and work as intended is not necessarily true, deck height varies as do many other things!)